1. Technical Field
The present invention is intended for a molded case circuit breaker for protecting a low-tension power distribution facility, such as an electric motor, from an overcurrent. The present invention relates to interior accessories (e.g., optional components), such as an ancillary switch for detecting the ON/OFF status of a primary circuit contact point and a tripping action, a circuit breaker equipped with an alarm switch, and their accessory switches.
2. Related Art
As shown in FIG. 7, reference numeral 1 designates a case (plastic mold case) of a circuit breaker. The case 1 houses a breaking section 2 of a main circuit, a toggle-link-type open-close mechanism section 3, and a tripping section 4. The open-close mechanism section 3 is coupled to an assembly (not shown) of a movable contact of the breaking section 2 in combination with an open-close lever 6. The open-close lever 6 is pivotally actuated by means of actuation of the open-close mechanism section 3, thus switching the contact of the main circuit. When a handle 5 is manually moved to an ON/OFF position, a toggle link mechanism of the open-close mechanism section 3 is actuated, thereby opening or closing the contact of the main circuit of the breaking section 3. As is well known, in the event of inflow of an overcurrent to the main circuit, the open-close mechanism section 3 causes tripping section in accordance with a signal output from the tripping section 4, thus opening the contact of the main circuit.
Accessory switch housing sections 1a and 1b are provided side-by-side on the upper surface of the case 1. An ancillary switch 7 and an alarm switch 9, which are of cassette type, are to be connected to the respective accessory switch housing sections 1a and 1b. 
In addition to the pivotal open-close lever 6 which opens and closes the contact of the main circuit of the breaking section 2, the open-close mechanism 3 of the breaker main unit is provided with an alarm output plate 8 which is slid in conjunction with tripping operation of the breaker. Two pairs of output protrusion 6a and output plate 8a are provided such that one pair protrudes so as to oppose one of the accessory switch housing sections 1a and 1b and such that the other pair protrudes so as to oppose the remaining accessory switch housing section. The output protrusion 6a of the open-close lever 6 and the output protrusion 8a of the alarm output plate 8 are provided side-by-side so as not to cause interference therebetween.
FIGS. 8A through 8C show the buildup structure of the open-close mechanism section 3. The open-close lever 6 pivots around a spindle 6b by means of operation of the open-close mechanism section 3. In synchronism with pivotal movement of the open-close lever 6, a pair projection which consist of the left-side and right-side output projections 6a and project from a frame of the open-close mechanism section move vertically. The alarm output plate 8 effects guiding and supporting action in a vertically movable manner along the frame of the open-close mechanism section 3. In a steady state, the alarm output plate 8 is retained and locked in an illustrated lower position. A latch is disengaged from a latch receiver 3a of the open-close mechanism section 3 in accordance with an output from the tripping section 4 (see FIG. 7), thereby causing tripping operation. As a result, a toggle shaft 3b of the open-close mechanism section causes pivotal movement, thus releasing the alarm output plate 8 from a locked state. The alarm output plate 8 is susceptible to spring force of a constriction spring 8b, thereby causing upward sliding action. As a result, the output projections 8a formed on both legs of the alarm output plate 8 are moved upwardly.
The ancillary switch 7 and the alarm switch 9 provided in the accessory switch housing sections 1a and 1b are constructed such that operation levers coupled to movable contacts project from the front surface of a unit case having a contact mechanism incorporated therein. In a state in which the ancillary switch 7 and the alarm switch 9 are provided in the breaker case 1 (see FIGS. 7A and 7B), an operation lever projecting from the ancillary switch 7 opposes the output protrusion 7a of the open-close lever 6, and an operation lever projecting from the alarm switch 9 opposes the output protrusion 8a of the alarm output plate 8. When the circuit breaker is turned ON/Off or tripped, a mechanical signal is transmitted to the ancillary switch 7 by way of the output protrusion 6a of the open-close lever 6, and a mechanical signal is transmitted to the alarm switch 9 by way of the alarm output plate 8. As a result, the switches are actuated in accordance with the signals, thus outputting electric signals to the outside of the circuit breaker.
The illustrated example shows a case where the alarm switch 9 and the ancillary switch 7 are provided in the accessory switch housing sections 1a and 1b of the case 1. There may also be possible to use the circuit breaker by means of providing the ancillary switch 7 into the accessory switch housing sections 1a and 1b without use of the alarm switch 9.
The output signal transmission mechanism of related-art structure has the following problems:
(1) The pair of output protrusions 6a are formed in non-symmetrical positions on the open-close lever 6 so as to match the positions of operation levers of the ancillary switches 7 provided in the accessory switch housing sections 1a and 1b. For this reason, as shown in FIG. 8B, the output protrusion 6a assumes a complicated stepped geometry.
(2) The alarm output plate 8 is provided along the exterior of the frame of the open-close mechanism section 3 and effects guiding and supporting action in a vertically slidable manner without involvement of occurrence of interference with the open-close lever 6. By means of the a toggle shaft and a drive spring of the open-close mechanism which causes pivotal movement at the time of tripping operation, the alarm output plate 8 is actuated. Therefore, the alarm output plate 8 assumes a complicated geometry and a complicated guide mechanism. Hence, the number of parts constituting the alarm output plate 8, the number of processes for assembling the alarm output plate 8, and the space occupied by the alarm output plate 8 become large. In terms of operation, friction or abrasion of components of the guide mechanism stemming from sliding action is apt to cause resistance or rattle, thus posing difficulty in ensuring smooth operation over a long period of time.
The present invention has been conceived in light of the foregoing drawback and is aimed at solving the foregoing drawback and at providing an improved circuit breaker capable of accurately transmitting a mechanical signal output from a breaker main unit to an ancillary switch and an alarm switch provided in accessory switch housing sections of a breaker case, with use of a simple mechanism and stable operation.
To achieve the object, the present invention provides a circuit breaker including:
a breaker case;
left-side and right-side accessory switch housing sections for housing accessory switches of cassette type; that is, an ancillary switch for detecting an ON/OFF state of a contact of a main circuit by means of an electric signal and an alarm switch for detecting tripping operation by means of an electric signal; the ancillary switch being opened/closed in conjunction with an output protrusion formed on an open-close lever of an open-close mechanism for opening/closing a contact of a main circuit; and
the alarm switch being opened/closed in conjunction with an alarm output plate which operates in accordance with tripping action of the open-close mechanism, wherein
a symmetrically bifurcated output protrusion is provided on the open-close lever so as to oppose an operation lever of the ancillary switch provided in the accessory switch storage section, and an extremity of the alarm output plate is caused to oppose an operation lever of the alarm switch which is provided as a pivotal lever coupled directly to the open-close mechanism and is to be provided in the accessory switch housing section in a direction orthogonal to the open-close lever.
Preferably, a case for an ancillary switch and a case for an alarm switch are made identical in shape with each other; a step is set between an operation lever of the ancillary switch protruding from a front surface of the case and an operation lever of the alarm switch, with reference to a thicknesswise direction of the cases. Further, the operation lever of the ancillary switch is caused to oppose a bifurcated output protrusion of the open-close lever and the operation lever of the alarm switch is caused to oppose an alarm output plate, while the ancillary switch and the alarm switch are provided in the breaker cases.
By means of the foregoing configuration, ends of the bifurcated output protrusion formed in the open-close lever correspond to the respective accessory switch housing sections formed on the breaker case. As a result, an ancillary switch may be provided in any one of the switch housing sections or in both the switch housing sections. Since the bifurcated output protrusion is formed symmetrically, the open-close lever per se assumes a simple geometry and can be manufactured inexpensively.
The alarm output plate is formed into a pivotal lever coupled directly to the open-close mechanism for opening/closing a contact of a main circuit. Hence, there is necessity for a complex linear guide mechanism, and accurate transmission of a mechanical signal output from the open-close mechanism to the alarm switch without involvement of transmission loss. Further, the lever-shaped alarm output plate can be made more compact than an alarm output plate of related-art structure. A step is provided between the operation lever of the ancillary switch and the operation lever of the alarm switch with reference to a thicknesswise direction of the circuit breaker. Hence, the lever-shaped alarm output plate can be arranged without involvement of occurrence of interference with the output protrusion of the open-close lever.